Psychophysiological and Metabolomics Responses of Adults during Horticultural Activities Using Soil Inoculated with Streptomyces rimosus: A Pilot Study

Abstract

This study compared the physiological effects at a metabolomics level with autonomic nervous system responses in adults during soil mixing activities, based on the presence or absence of Streptomyces rimosus in the soil. Thirty adult participants performed soil mixing activities for 5 min using sterilized soil with culture media and Streptomyces rimosus, respectively. Blood samples were drawn twice from each participant after each activity. Electroencephalograms were measured during the activity. Serum metabolites underwent metabolite profiling by gas chromatography, followed by multivariate analyses. Serum brain-derived neurotrophic factor and C-reactive protein levels were measured by Enzyme-Linked Immunosorbent Assay. Soil-emitted volatile organic compounds were identified via solid-phase microextraction and gas chromatography–mass spectroscopy, followed by multivariate analyses. The volatile compound analysis revealed that the terpenoid and benzoid compounds, geosmin, and 2-methylisoborneol were greater in soil with Streptomyces rimosus. Serum metabolomics revealed that the treatment group (soil inoculated with Streptomyces rimosus) possessed relatively higher levels of serotonin compared to the control group (soil mixed with culture media), and serum C-reactive protein levels were significantly lower in the treatment group. In the treatment group, the electroencephalogram revealed that alpha band activity of the occipital lobe increased. This study concludes that Streptomyces rimosus soil contact can positively affect human metabolic and autonomic reactions. Therefore, this pilot study confirmed the possible role of soil microorganisms in horticultural activities for psychophysiological effects in humans.

Psychophysiological Responses of Humans during Seed-Sowing Activity Using Soil Inoculated with Streptomyces rimosus

“…After collecting raw data with a GC-TOF-MS device for lysed serum samples, GC-TOF-MS data were digitized using ChromaTOF software (version 4.44, LECO Corp., St. Joseph, MI, USA) and Metalign program, and data processing such as peak selection, alignment, and baseline correction was performed [ 23 , 35 ]. Multivariate statistical analysis was performed on the data quantified through the Metalign program using SIMCA-P+ (Ver.…”

“…Soil microorganism Streptomyces rimosus (S. rimosus) is a bacterial species of the genus Streptomyces commonly found in soil. In addition, S. rimosus has also been shown to release large amounts of geosmin and 2-methylisoborneol (2-MIB) [ 23 ], which are the major volatile metabolites of common earthy odor [ 24 ]. A study measuring the effect of olfactory stimulation of these components on the psychophysiological responses of adults showed that alpha wave activity increased in the brain’s frontal lobe, which positively affects emotional stability [ 15 ].…”

“…Another soil microbial species, Mycobacterium vaccae (M. vaccae) , is a non-pathogenic bacterial species belonging to Actinomycetales . In a recent study, using soil inoculated with M. vaccae [ 27 ] and S. rimosus [ 23 ] for adults, soil mixing was performed for 5 min and EEG and metabolic responds were analyzed. As a result, alpha wave activity increased in the occipital lobe of the brain, showing a psychophysiological stabilizing effect [ 27 ].…”

“…As a result, alpha wave activity increased in the occipital lobe of the brain, showing a psychophysiological stabilizing effect [ 27 ]. In addition, serotonin was found to increase significantly in blood metabolite analysis [ 23 ]. It has been reported that soil mixing activity using soil microorganisms can lower anxiety and stress and increase vitality.…”

“…However, all of the above studies have limitations in that just one motion (soil-mixing) was repeated only for 5 min, and the adequacy of the intervention time could not be verified. In order to identify the psychophysiological mechanism according to the presence or absence of soil microorganisms, it was suggested that additional studies according to the difference in intervention time, frequency, and activity are needed [ 23 ].…”